Mount Prospect, Illinois 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

294
FXUS63 KLOT 291901
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
201 PM CDT Mon Jun 29 2026

.KEY MESSAGES...

- Dangerous heat wave will continue through at least Wednesday
  with daytimes highs in the 90s and peak afternoon heat indices
  of 100 to 110 degrees.

- Dangerous heat may continue into Thursday, though forecast
  confidence is lower due to the potential effects from storms.

- Thunderstorm chances will begin to increase late in the week,
  likely bringing some heat relief for at least some areas.

- While likely not a complete wash out, there will be periodic
  chances for thunderstorm through the holiday weekend.

&&

.DISCUSSION...
Issued at 1253 PM CDT Mon Jun 29 2026

A strong upper ridge over the Ohio Valley will move very little
through Wednesday setting the stage for a continuation of the
heat and humidity. Most guidance depicts 925mb temps warming
another 1-2C Tuesday, so high temps will likely be a couple/few
degrees hotter than today. A strong low level inversion has
limited the depth of mixing today and forecast soundings suggest
a similarly strong inversion Tuesday. This strong inversion
limiting mixing plus the beginnings of evapotranspiration (ET)
season has resulted in dewpoints higher than pretty much all
available guidance today. We are about a week away from reaching
50% peak from corn, so while it is still early, it likely is
still a contributing factor. Given this, I continued to trend
dewpoints toward the high end of the guidance spectrum Tuesday,
which could push heat indices locally to around 110F degrees in
the afternoon.

By Wednesday, there are signals in the models that deeper mixing
could result in somewhat lower dewpoints, but higher air temps.
The net result may be heat indices a couple/few degrees lower
than Tuesday, but air temps potentially reaching into the upper
90s any slight improvement in heat indices will be more
academic. If guidance ends up being too aggressive in mixing out
dewpoints Wednesday, then another day with heat indices of 105
to 110F would occur.

The heart of the upper ridge is expected to drift eastward some
Wednesday night into Thursday which would place our area
precariously close to the proverbial "ring of fire" convection.
Most available guidance keeps convection north of the area
through much of the day Thursday, which would result of a 4th
consecutive day of heat indices of 100-110F. This would trigger
an Extreme Heat Warning area-wide, since the warning criteria
includes 4 consecutive days of advisory level heat indices.
Pondered the upgrade/extension into Thursday, but opted to hold
off for now given some lingering uncertainties with respect to
potential convection, convective debris cloudiness, and/or
outflow potentially disrupting the heat Thursday. Guidance is
very often too far north with convection/convective effects in
these type of set-ups, so while the signal is pretty strong
for another day of dangerous heat Thursday, still think it is
possible that at least part of the area could see some relief
Thursday due to convection and/or convective effects.

A more active pattern is expected Thursday night through the
upcoming holiday with at least periodic chances for showers and
thunderstorms. There will likely be many dry hours, but an MCS
or two will likely traverse the region at some point this
weekend.

- Izzi

&&

.AVIATION /18Z TAFS THROUGH 00Z WEDNESDAY/...
Issued at 1224 PM CDT Mon Jun 29 2026

Only forecast concern this period are the winds. South/
southwest winds have been slow to increase late this morning
into early this afternoon but gusts into the lower/mid 20kt
range are still expected this afternoon. Directions will turn
more southerly with sunset this evening and gusts into the
15-20kt range will be possible overnight, mainly across the
urban Chicago area where temps will be warmer. Low level winds
will steadily increase overnight and low level wind shear will
be possible, mainly west of the Chicago terminals. Directional
changes in the low levels may be more of a concern than the
speeds and low level wind shear mention will need to be
monitored with later forecasts. Southwest winds will increase
mid/late Tuesday morning, back into the lower/mid 20kt range.
There is some potential for wind gusts into the 30kt range by
late Tuesday afternoon.

Earlier ifr/low mvfr cigs have steadily lifted with some high
mvfr cigs still possible for the next 1-2 hours, but overall
expecting prevailing vfr cigs that will scatter out later this
afternoon. The low levels will remain quite moist overnight into
Tuesday morning and not expecting another period of lower cigs
Tuesday morning, but trends will need to be monitored. cms

&&

.CLIMATE...
Issued at 252 AM CDT Sun Jun 28 2026

     .Daily Records for the Upcoming Week........

Chicago (KORD)
            Record High       Record Warm Minimum
June 29       97 (1954)            80 (1931)
June 30       99 (1953)            80 (2018)
July 1       103 (1956)            78 (1931)
July 2        99 (1970)            79 (1911)
July 3       102 (1949)            78 (1911)
July 4       102 (2012)            80 (1921)


Rockford (KRFD)
            Record High       Record Warm Minimum
June 29      103 (1931)            75 (1931)
June 30      102 (1931)            76 (2018)
July 1       101 (1931)            76 (1970)
July 2        99 (1910)            74 (1970)
July 3        99 (1925)            75 (2012)
July 4       102 (2012)            77 (1977)

NWS Chicago

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...Heat Advisory until 10 PM CDT Wednesday for ILZ003-ILZ004-
     ILZ005-ILZ006-ILZ008-ILZ010-ILZ011-ILZ012-ILZ013-ILZ019-
     ILZ020-ILZ021-ILZ023-ILZ032-ILZ033-ILZ039-ILZ106-ILZ107-
     ILZ108.

     Extreme Heat Warning until 10 PM CDT Wednesday for ILZ103-
     ILZ104-ILZ105.

IN...Heat Advisory until 10 PM CDT /11 PM EDT/ Wednesday for INZ001-
     INZ002-INZ010-INZ011-INZ019.

LM...Small Craft Advisory until 10 PM CDT this evening for the IL
     nearshore waters.

&&

$$

Visit us at weather.gov/chicago